Automatic telephone system.



A. J. RAY. AUTOMATIC TELEPHONE SYSTEM.

V APPLICATION FILED JUNE 16, i953. lp-LLQ TTQfm-Era WTA/E55 A. 1. am. AUTOMATIC TELEPHONE SYSTEM.

APPLlCTlEi HLED JUNYE i6. 1913.

Patint/d Apr. 16, 1918 5 SHEETS-SHEET 3.

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A. I. RAY.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION' FILED JUNE I6. 1913.

PafcenI/ Apr. I6, I9I8.

5 SHEETS-SHEET 4.

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I/I/JTNESSES I. RAY.

AUTOMATIC TELEPHONE SYS'I'EIVI.

APPLICATION FILED JUNE I6, IBIS. Patented Apr 16,

/I//T/VESSES brrr-ran srarns rennen? oracion.

ARTHUR J. RAY, 0E* CHICAGO, ILLNOS, ASSIGNOR T0 AUTOMATIC ELECTB'JiC COMPANY, 01? CHICAGO, ILLINOS, A CORPORATION 0F ILLINOIS.

AUTOMATC TELEPHNE SYSTEM.

Specicaton of Letters Patent.

Patented Apr. to. iQt.

applicati@ fue@ June is, 191s. serial No. 773,930.

course, desirable that these calls be given l preference over local calls. Thus, where two subscribers are engaged .in a local connection and one of these subscribers is desired in a long dist-ance call, some means should be provided for notifying the desired subscriber of this fact. If the operator attempted to make connection with the line with the ordinary connector switch,` she .would merely receive the usual busy signal, without establishing a talking connection with the subscriber, and thus be unable to inform bini of the fact that he was wanted in a long distance call, Heretoforc, special connectors have been provided by using which the operator could obtain connection with the busy subscriber-s line. lt would, of course, be inadvisable to interrupt a long distance connection to advise the subscriber that hewas wanted in a second such connection. T here'fore, in these previous systems it was necessary to provide aditl'erential busy test so that the operator, in first. establishing connection through the ordinary connector, could determine whether the desired line was engaged in a local connection or in another long distance conncction. Then, after ascertaining that the line was engaged in. a local connection, she had to release that connection and employ a special connector in order to establish connection with the desired line.

'lhc object ot' my invention is to provide a connector switch which. when employed in regular automatic or local service; operates in the usual and well-known manner. When a connection is extendedto this connector, however, from an operators board, means are provided in the connector whereby the operator'y can establish connection with a line which isinvolved in ay previouslecal connectlon, but cannot obtain connection with a line which is. involved in an estabhshed long distance connection. n other' words, by the use of this improved con# ai nector,the operatoryat the long distance' b oard can obtain connection with 'alibusy@ lines, except those which are involved'in-fan established connection from a long distancia? board, in order to advise these subscribers that they are wanted in a long distanfcoconnection.

These and other objects of my inyentob,

will be more readily understood by reference .i

to the accompanying drawings, 1n whichf have illust-rated my invention in connection' with automaticI and manual apparatusco well-known types.

In the drawings Figure-1 represents a diagrammatic layout or a telephone system in which have chosen to illustrate my ventlon.

Figs. 2 and 3 show a complete connection( between a calling subscriber at substation A. and a called subscribers line. Fig. el shows a manual telephone line an lan operators cordcircuit.

Fig. 5 is an automatic selector switch, through the medium of ,which an operator extends a connection from the cord circuit.

The telephone system illustrated in Fig. l comprises an automatic exchange and a manual exchange. The manual exchange is represented by a switchboard XV comprising a plurality ot' operator-s positions W. At T and T2 are shown groups of substations T the lines ot' cach of which substations terminate in an answering jack J on one operat0r`s position l l and in a multiple jack J on each operator-'s position inthe usual and welldmown manner. 'Suitable cord circuits M are provided for establishing connections.

The automatic exchange is of a wellknown type comprising subscribers individual presclector switches C, first selector' i100 lines capacity. The subscribers substations 105 A are divided into groups A2, A3, A4, etc., usually of one hundred lines each. On a scale of three to ten, therefore, the three groups A2, A3 and A4 represent one'coinplete thousand and the groups A, A", and A7 reprc- 110 lo These levels are represented by horizontal lines which entend across and beneath all the switches of a group to indicate that correspondinglcontacts of alli the switches are multipledttogether. All the line switches C A belonging' to one group ot' subscribers lines have common access to a group of first selectors E. lThe bank contacts of the first selectors E of corresponding groups or hundreds are multiplied throughout the differ# ent thousands. r1`he first level of these first selectors is connected to trunk, lines leading to second selector switches F associated with the first thousand, the second level of the first selectors is connected to trunk lines leading to second selectors associated with the second thousand, etc. The bank contacts oi all (the second selectors F associated with a given thousand are multipled together, and the rst level is connected to trunk lines so leading to'connector switches H which have access 'to the subscribers lines of the rst hundred of that thousand, the second level is connected to trunk lines leading to connectors which have access to the lines of the second hundred, etc. This trunking arrangement of an automatic exchange is in general weil known in the art, and it is not thought necessary to describe it in further detail herein. ce ln order to form a means of communicai. between the automatic and manual eX- f there are rovidcd a number of Y nnesleading trom multiple jacks J2 .e manual exc range to selector switches automatic exchange, which selectors lrrespond in function to the subscribers 'i 1st selector switches E. The bank contacts of the operators selectors 1 may be multipled? with those of someof the subscribers seco -lectors FE, as indicated.

vAlthcaigh inthe above descrlption of the system shown in Fig. 1 reference has been made to an automatic exchange and' to a manual exchange, it is to beundcrstood that this does not mean thatJ the manual part of the system is necessarily a separate and distinc't exchange. It may be simply a manual switchboard which is usually installed in automatic exchanges orthc purpose of hanV- to (lling long distance or toll calls.

` 1n Figs. 2, 3, l and 5 the different parts of the apparatus aredesignated by the same reference characters, in so far as is consistent, as in the diagrammatic Fig. 1. The automatic substation A (Fig. 2) com- ,eral type of master switches shown in Britla call register 2S which is controlled by a prises the usual receiver 2, transn'iitter 3, ringer a and condenser 5. licing an automatic substation, it is also provided with a suitable call-sending mechanism for controb ling the automatic switches, which mechanism is represented.'diagrammatically by a pair of impulse springs 0 and 7 and an impulse wheel 8, which latter may be controlled in a `Well-known manner through the medium of a dial provided with linger holes in such a way rthat the impulse springs may be momentarily separated a number or' times corresponding to the respective digits of the number of the called subscriber.

The subscribcrs individual switch C is of ao the general type ot' subscribcrs switch shown in British pat nt to ll. Vv. lames No. 26,301 of 1906, resembling more closely, however, the particular type shown in British patcnt to T. G. Martin No. 14119 ot 1910. This line switch comprises, among other details, a plunger (not shown) attached to the end of a so-called plunger arm 9 controlled -by a magnet 10, which magnet comprises an operating winding 11 and a holding wind- 90 ing 12. rlhis magnet also controls the cutol armature 13. The winding l1 operates both the plunger arm 9 and the armature 13, while the winding 12 is strong enough only to Operate thc armature 13 and to hold 95 the plunger arm 9 in its operated position. WV hen the plunger arm 9 is operated its plunger is forced into a bank of contact springs, forcing the springs 14, 15, 16 and 17 into engagement with the springs 18, 19, 20 and 21, respectively. Although only one set'of springs, namely 14C to 2l, inclusive,

is shown, each line Switchis provided with a plurality of such sets, each set forming the terminal of a trunk line leading to a first selector switch E. Each trunk line is conne'cted in multiple with corresponding springs of all the line switches of the group which is controlled by the master switch l). The switch C is controlled by the subscriber .through the medium ,of the line relay 22,

which relay is preferably slow acting-that is, slow to release its armature upon dcnerglzing. The master switch D is of thc=genish Patent No. 26,301 of 1906, ureferred to above, being, however, of the particular type disclosed in British Patent No. 1419 of 1910, also referred to above. lThe function of the master switch, as iswell known, is to maintain the lungers of all the idle line switches in position to engage the terminal of an idle trunk line.

Associated with the line there is shown double-wound magnet 29. i The Erst selector switch v.E is ,of the genn eral type of selector switches disclosed in United States Letters Patent No. 815,321,fv granted March 13, 1906, toleith, Erickson and Erickson, except Ythat the so-called side switch is omitted. Among other details, the selector E comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wipers 30, 31 and carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 33 and a rotary motion controlled by the rotary magnet 3l. 'The operations ot the switch are controlled through the medium of the double-wound line relay Means for permitting the switch to be restored to normal position are provided in the release magnet 3G, which, upon energizing, withdraws the retaining pawls 'from the shaft. The spring contacts 37 and 3S are permitted toclose only when the switch shaft has been raised one or more stepsi'rom its lowest position. rlhe relays 3.() and l0 are slow acting relays-that is, relays which decncrgize slowly after 'their energizing circuits are broken. rl'his slow action is usually obtained by placing a ring of copper around .one end ot' the core of the relay.

The second selector F, as well as the selector l (Fig. o), is the same as the selector E.

The connector switch H (Fig. is ofthe general type of connector switches disclosed in United States Letters Patent No. 815,176, granted March i3, 1906, to Keith, Erickson and Erickson, the circuits being modified,

however. to ada t the switch to o )crate inl a system in which the central oilice apparatus is controlled by impulses delivered over the two sides of the line in series. Like the selectors, the connector is provided with a shat't (not shown) carrying the Wipers 41, 42 and 43, which shaft is controlled by the vertical magnet 44 and the rotary magnet 45. The usual side switch comprising the wipers 4o, 47, 48 and #t9 is controlled by the vprivate magnet 50 in the usual and ywellknown manner. The magnet 250 is the usual release magnet. The line relay 51 is connected with the line through the reversing springs of a .so-called back-bridge relay 52, through the windings of which latter relay thc called line is provided with talking current. The application of ringing current to the called line is controlled by the ringer relay 253. At Q there is .shown a busy signaling machine which is connected through the Contact ot springs 20T and 20H of the relay 53 with the spring of the relay 54, the function oi which Ais to send, under certain conditions, a busy tone back over the line. The complete operation ot this relay will be described later. The busy signaling machine, as represented herein, comprises an induction coil or transformer, the primary winding'o'tl which isV included in a local circuit with a battery and two interrupters, one ot high frequency )2 plug l calling and and one of low frequency. Through the medium of these intcrrupters an intermittent interrupted current is supplied to the primary winding, which induces an intermittent. alternating current in the secondary winding, whereby, when said winding is connected with the subscribers line, an intermittent buzzing sound is heard in his rcce'iver.

rllie substation T (Fie. l) is an ordinary local battery manual substation comprising a transmitter 55, receiver 56, induction coil 5T, magneto 58 and ringer 59. At the central oitice the line is provided with the' usual answering jack J, one or more mltiple jacks il', vthe line relay 60, cut-oit' relay 6l, line lamp 62 and a visual busy signal 63 associated with each multiple jack. The operators cord circuit M resembles the usual cord circuit employed in manual systems in that it comprises an answeringplug P', a calling answering supervisory lamps G5 and 66 and suitable relays for controlling the circuits thereof. The relay 67 in the calling end of the cord is a polarized relay. As shown, this cord circuit is adapted to complete connection with either another manualsubstation, such as the substation T, or with a trunk line leading to the automatic exchange, or with an ordinary common battery line. l/Vhen the relay 68 is in its normal position, the circuits of the relay 67 are adapted for use in connection with a local battery line, or with a trunk line leading to the automatic exchange; but when the relay 68 is energized, the circuits of the relay 67 are adapted tor use in connection with va common battery manual line, or a similar line.

The trunk lines which lead from the manual switchboard to the automatic eX- change, as has been explained in connection with Fig. 1, terminate in the multiple jack J2 on the manual switchboard. The sleeve conductors of the rjack J2 are connected to battery through a relay 69 which controls the springs of a visual busy signal 70 associated with cach multiplo viack. I

For the purpose ot supplying cuirem1"tor operating the central otlice apparatus and Jfor talking there is shown a plurality of batteries B having one terminal grounded at G. ln practice, however, only one battery need beaised, or. preferably, one in each exchange. l

'A general description ot' the apparatus having been given, it will now he explained how connection can be established between the line of substation A and another substation line, the telephone and line switch of which are not shown in the accompanying drawings,.b'ut which may be the same in detail' as the telephone or substation A and line` switch C. The number ot' the called line Wewill assumeto be 2220. Since the autoinatic switching apparatus disclosed herein is in general Well known in the art, and is described. in the publications herein referred to, its operation will be explained in a more or less general manner. Upon the removal of the receiver from the switch hook at the substation A preparatory to making a call, the talking circuit of the substation is bridged across the line conductors 71 and 72 by the switch hoolrsprings 73 and 74:, whereby the circuit of the line relay 22 of the switch C is'closed. rlhis circuit extends from ground G2 through the springs 75 and 76, line 71, substation A, line 72, springs 77 and 78 and the relay 22 to the battery lead 80, thence through battery B and to ground G. The relay 22, upon energizing, closes the circuit of the operating Winding ll, which operates 'through the medium oi' the armature 13 to disconnect the relay 22 from the line and to thrust the E is thereupon energized overa circuit eX- vtending :from ground Gs through the lower Winding of said relay, backcontact of the switching relay sprihlg 82, thence over the heavy conductors to and through the substation A and back over the other side of the line, through the let-handrwinding of the meter magnet 29, back contact of the switch-l ing relay spring '83 of the selector and the upper Wziding of the line relay 35 to the battery ad 80. The relay 35, upon energizing, closes the circuit of the relay 89, `which in turn, upon energizing, closes a circuit extez-.iding from ground G4 through the springs 85., line switch bank springs 2O and 16 and the holding Winding to the battary lead 80. The energization oi' this Winding serves to hold the switch@ in its operated position after the circuit of the Winding 11 is broken by the relay 22, which deenergizes shortly after it is disconnected from the line. ril`he energizationof the relay 39 at the selector E also completes'a circuit Aextending from ground Grt to the springs 85, 29 and 16 and through the righthand Winding of the meter magnet 29 to ther battery lead 80. The current in this Winding is in opposition to the line current loW- ing through the'other Winding, and the mag net is therefore not operated at'this time. At the saine time a guarding potential is eX- tended from ground Gt at theselector to the connector private bank contact 23a of the calling line in the bank oit each of the connector switches which have access thereto. Upon the closure of the springs 17 'and 21 'by the operation of the switch @,the inaster switch D operates in a Well-known' reanrecae/is ner to advance the plungers of the idle line switches to a position. opposite an idle trunk line.,

The calling subscriber nowoperates his calling device for the first digit 2 of the ,To called number, whereby the substation iinpulse springs 6 and 7 are separated twice momentarily, each time breaking the circuit of the selector line relay 35. 'lhe relay 39 of the selector being slow acting does not dete energize during the momentary interruptions et its circuit by the relay 35, and con-- sequently each time the latter relay denergizes, an impulse is transmitted over the circuit ex'tending from ground G5 through the ao springs '88 and 89, 90 and 91, spring 92 and its front contact, relay 4l() and the vertical magnet 33 to the battery lead 80. The ver tical magnet receives two impulses over this circuit and operates to raise the switch shaft and Wipers tWo steps Ato a position opposite the second row or level of banlr contacts, ,i and at the saine time the shaft-controlled contacts 8? and 38 are closed. The slow act ing relay l0 is maintained in its energized eo position continuously While impulses arel being transmitted to the vertical magnet through it, and in its energized position closes a circuit extending tronigroundl Gr f through the springs `93 and 94 andthe relay 95 95 to the battery lead 80. The" relay 95, upon energizing, `forms a locking circuit for itself extending from ground G4 at the relay 39, through the springs springs 96 (which are controlled by the rotary magnet 34), shaft contact 37 and the springs 9'? and 98 and the Winding of the relay 95 to the battery lead 80. rilhus upon the deenergiaation of the relay l0 after the last impulse is delivered te the vertical magnet, the relay reniains energizedA and the circuit oit the/ rotary magnet 3ft is closed, which circu .e141- tends from ground G4 at the rel/ayy 39 through the springs 85, 95, 37, 9'?, 99," 99 and 100 and the magnet to the battery iis lead 80. The inagnet 3ft, upon/energizing',

rotates the Wipers one step, and by opening thek spring contacts l0@ and .96 disconnects, theiground G4 troni itself and from thei., relay 5 lf the first trunk line of the sec- M5 'ond level isidle, the relay 95 de'energiaes as soon' as the spring contact 96 is opened lit this trunkline is busy, however, the private Wiper 32`iinds theontact which it engages provided with a guarding ground potential '12o which is transmitted to 'the relay 95 through its springs 97 and 98, and thereby prevents it from denergizing. The magnet 3ft, how ever, delinergizes when the springcontact l0@ is'brolren, regardless whether the 3.25 lay ,95 remains energized or not li re ay 95 remains energized, he circuit ci: the rotary .magnet `will be a tin closed as 'soo-n as its armature drops haci; tarfenough ytoclose the jcontacts 109, and 96. j The rotary i3 i the relayl 95 denergizes.-

the non-grounded contact of an idle trunk line is reached by the wiper '52, whereupon The relay 05, upon denergizing, whether after one or several operations of the rotary magnet, permanently breaks the circuit of the mag- -net 34 and closes the circuit of the switching relay 101, which. circuit extends from ground Gr4 through the springs 8.3, 06, 37, 97, 102 and the relay 101 to the battery lead 80. The relay 101, upon energizing, disconnects the line relay from the line and entends the line connection over the 'heavy conductors shown through the wipers and 31 to the second selector F. The line relay 103 of the switch F thereupon becomes nal energizing circuit is broken by the relay 39, which denergizes shortly after the line relay 36 is disconnected from the line. The relay 10e oftthe selector 'F also maintains a guarding ground potential upon the private I 'bank contacts of the trunk line 'in the banks 'of the iirstlselector switches E 'which have access lthereto.`

.ilff'hen the substation calling device is operated for the second digit 2, the selector F operates in the same' manner as explained for the selector E lto extend the connection over the trunk conductors107, 108 and 109 111.,.101 and'12 of the switches F,.E and` C, respectively. This circuit extends from ground G8 at the connector switch through the relay 53, springs 112, conductor 109, wiper 113, thence through the springs 114 `and 115 and relay 111 to the battery lead 80 and also through the contacts 116 and 117, wiper 32 ots'elector E and through the relays 101 and 12 over the circuits already' traced. The right-hand winding of the meter magnet 29 is also included in the circuit in multiple with the relays above mentioned. rEhe switching relays 111 and 101 of the switches F and E, the cut-oit windw ing 12 of the switch C and the right-hand winding of the meter magnct'29 all have a comparatively high resistance, as compared l with that ci the relay 53" of the connector switch, so that the latter, relay is not operativelyenergized over this c1rcuit. l

. 1when the substation callingv device 1s operated for the third digit 2, thc circuit or theA connector line relay 5l is broken twice. Since the relay 110 is slow acting' it does not dccnergizc during the momentary interruptions of its circuit by the relay 51, so that each time the latter relay is deenergized, a circuit is closed extending trom ground G through the spring 118 and its back contact, spring 110 and its front contact, relay 120, vertical i'nagnet 44 and side switch wiper 40 to the battery lead 80. The vertical magnet 4.4 receives two impulses over this circuit and operates to raise the switch wipers 41, 42 and 13 to a position opositc thel second level of bank contacts. The relay 120, which is included in series with the vertical magnet, remains in its energized position during the entire time that impulses are being transmitted through it and operates to close the circuit of the relay 122 and the private magnetO. After the last impulse is delivered the relay 1-20 opens the circuit of the private magnet 50, which, upon denergizing, permits the side switch to advance from first to second position. The movement of the side switch wiper 49 from first to second position transfers the battery connection from the vertical magnet to thc rotary magnet 45. The calling subscriber now operates his calling device for the last digit 0, in response'to which the connector line relay 51 operates to transmit ten impulses through the rotary magnet 45,

in scries'with the relay 120, whereby the shaft wipers are rotated onto the contacts of the desired line. The relay 120 operates in response to the impulses for this digit in the same manner as for the previous digit'to cause the privato magnet 50 to advance the side switch one more positionthat is, from second. to third 1)0sition--after the last impulse for the digit is transmitted.

By the engagement of the side switch wi pers -16 and 47 with their tl'lirdfposition contact points, and by the denergization oii the rel lay 122, the line connection is iinally completed with the called substation, as shown by the heavy conductors. rlhe relay 122 controls the contacts in the' line circuit and is made slow acting so as to prevent.- the completion of the line connection until after the cut-oliA winding-ot the called subscribers individual,switch has had time to op crate its armature to disconnect the switch Jfrom the line. This switch amlwinding correspond to the switch C of the calling subscriber and the winding l2. The springs thatarc actuated inthe called subscriber-s line or individual switch correspend to the springs 75, 76, 77 and 7S. rlhe 125 an operator in making a semi-automatic call can cut4 in on a connection regardless of whether said connection is busy or not. By the engagement oi' the side switch wiper 49 with its third-position contact point, the circuit of the ringing relay 253 is closed, which circuit extends from ground G1* through the interrupter 125, relay 253, springs 126 and side switch wiper 49 to the battery lead 80. The ringingrelay 253, upon energizing, disconnects the calling line from the called line and bridges the ringing current generator 127 across the called line to signal the called subscriber. The ringing relay is energized only intermittently through the medium of the interruptor 125. Upon the response of the called subscriber his line is c provided with talkin@- current through the windings of the back ridge relay 52 of the connector switch, which relay, upon ener-l gizing, closes the circuit of the ringing cutout relay 128, said circuit extending from -the battery lead 80 through the side switch wiper 49, relay 128, sprlngs 129 and 130 and the shaft-controlled contact 131 to ground G12. The relay 128, upon energiaing, interrupts the circuit of the ringing relay 53 at the springs' 126 and closes a locking circuit for itself through its own springs 132 independent of the ysprings of the back--bridge relay 52. A furtheriesult of the encrgization of the relay 52, uponthe response of the called subscriber, is the transposition of the connection between the windings of the line relay 51 and the trunk conductors 107 and 108, whereby the direction of current in the calling line is reversed. This reversal of the current in the left-hand winding of the subscribcrs meter relay 29 (Fig. 2) causes the two windings to` assist one another and the armature is attracted to operate the meter to register the call. l A

After the conversation is completed the connection is released by the hanging up of the receiver at the calling substation in `tbe following manner: When the receiver at the substation A is restored to the switch hook, the separation of the hook switch springs 73 and 74 destroys the energizing circuit ot' the connector line relay 51 (Fig. 8). 'lhe relay 51 thereupon denergizes 3G and 181.

Lacasse and opens .the circuit of the relay 110. The relay 110, upon denergizing, opens the holding circuits of the relays 111, 101 and 12 of the switches F, )E and C, respectively, at the springs 112 and also closes the circuit of the connector release magnet`250. The latter circuit extends from ground Gf through the spring 118 and its back contact, spring 119 and its back contact, shaft-con trolled contact 18() and magnet 250 to the battery lead 80. The magnet 250, upon energizing, restores the connector switch shaft and side switch to normal position, and its own circuit is interrupted at the contact 189 when the shaft reaches its lowest position.

The denergization of the relays 101 and 111 of the switches E and F serves to close the circuits of their respective :release magnets The circuit for the magnet 36 of the switch E extends/from ground G5 through the springs 88, 89, 90, 91, spring 92 and its back contact, shaft contact 38 and magnet 36 to the battery lead 80. The circuit of the magnet 181 is similar to that of the magnet 36. The circuits of the magnets 36 and 181 .are broken when the switch shafts reach their normal positions. The denergization of the winding 12 of the switch C permits the plunger arm 9 and armature 13 to restore to normal ,fisitioit From the above description it vis evident how connections are established and released in the automatig exchange. lt. will now be explained how an operator may .es tablish a connection between the manual telephone T (Fig. Ll) and an automatic substation. The subscriber'at the telephone 'l signals the operator in the usual manner by operating the magneto 58, whereby the line relay becomes energized and is locked in its operated position to close the circuit ot lamp 62. The locking circuit for relay G0 extends from ground (l13 through the back contact of armature 138, Contact point lill, armature 135 and right-hand winding ot' relay, G0 to the battery B. The operator answers the call by inserting the plug l" into the jack l, whereby the calling line is connect-ed with the cord circuit and a circuit is closed from ground G through the contact 137, armature `138 and its back contact, sleeve of therplug P and jack .l and Cut-oli' relay (3l to the battery B. 'lhe relay 61, n )on energizing, disconnects the line iclay rom the line, breaks the holding circuit of the line relay .and closes the circuit ofthe busy signals (33. Upon learning the number ot' the desired station, the operator inserts the plug P? into a multiple jack J2 of an idle trunk line leading to a selector switch l in the automatic'exchange, and operates the key K to connect a calling device similar to that at the automatic subscribers substation with thc trunk, in lig. 4 the calling device is rqpresented diagraming' circuit instead.

matically by a pair ot' impulse springs 1110. ly the engagement ol the sleeve conductors ot the pluglg and the jack J2 a circuit closed It'rom ground in the cord circuit through the upper windingl of relay 141, relay titi. plujr l. jack JP' and relay .(59 to the battery l. The relay Gti has a sutliciently high resistance to prevent enough current Vt'rom flowingoyer this circuit to energize the relay ($8: but it is itself ener- Zgizcd as well as the relay lei-1. The relay lll prepares the circuit for the lamp Gti, which circuit, however, is still open at the springs it?. of the key K. The relay G9, upon energizing, closes the circuit of 'the busy signals 70. The connection of the cord circuit with the selector l over the trunk conductors 115 and 146 causes the line relay 14.4' of said selector to energize in the same n'ianner in which the line relay of the selector E (Fig. 2) was energized when the connection was lirst extended to it from the calling substation. The operator now operates her callingi device in accordance with therespective digits of the number called for. rlhe selector I operates in response to the lirst. digit in the same manner as plained for the selector 1G (Fig. Q) to extend the connection to a second selector similar to the selector F (Fig. 2). This second selector operates in response to the Second digity to extend the connection to a connector switch, which in turn operates in respense to the last two digits to complete connection with the called line in exactly the same manner as when said switches are operated by an autbmatic subscriber, as hereinabove explained. Atter the operator at the cord M has completed the operation of the c; lling' device, the key K is restored' to normal position, whereby the calling device is disconnected from the line and the polarized relay 67 is bridged acrossthe talli- The current which flows through the relay G'at this time is of the proper direction to maintain the contact 148 closed, whereby the circuit oi the lamp (3G is completed, said circuit extendingl from ground G15 through the springs 142 of key K, contact 148, armature .19S and its front contactI and lamp GG to the battery B. Upon the response ot' the called subscriber, the current in the polarized relay 67 of the. cord circuit is reversed in the same manner in which the current, in the automatic substation was reversed. This reversal of current causes the relay (37' to open the contact 148, whereby the lamp (S6 is extinguished to signify that the called subscriber has answcred.

It will be remembered that in the connection described bet\\'een`tl1e automatic substation A and the called subscribers line the holding' circuits for relays 111 and 101 of the selectors F and ll were completed through the relay of the connector switch. In the same manner the holding circuit of the relay 149 of the selector l (nur.

is completed through the relay 53a oft' tlie connector when the operator makes a call. rllhe relay 1&9 of the selector l has a low resistance as compared with the corresl'ionding' relays ot the switches lf and E, so that when the relay 149 is included in the circuit ot the relay 53 of the connector, 'the latter relay olaratively eiuufgrized. attracting' its armature to separate the spring 191 from the spring' 19-lv and to make connection with the spring 195 to, at this point, close a circuit t'or the relay which circuit is open at the present time at the springs 196 and 19T and at the second-position contact ot side switch wiper 18. This circuit is the busy circuit and will be' described later, together with the complete operation of the switch when a` busy line is called. lVhenever an operator calls an automatic line, suticient current isl permitted to pass through the relay 53a for it to be operatively energized, but when an automatic subscriber calls an.- other automatic subscriber, the resistance of the coils 111 and 101 in series with relay 53a is too great to allow said relay to pull up: The object oit' this will also be explained later.

It haring been explained how connections may be completed with an automatic line, either by an automatic subscriber or by the operator, it will new be explained how connection is prevented from beim;` made with a busy line when an automatic subscriber is calling; also how an operator prevented 'from making` connection when the party she is calling is engaged in a long' distance call. Provisions are also made whereby the operator, upon calling` an automatic subscriber who is engaged in a local call, can cut in on the conversation without receivingr the usual busy tone.

Assuming' now that au operator is -callinp` an automatic subscriber who is engaged in a long distance call. lnother words, the subscriber whom the operator is calling is valready engaged in a call initiated by another operator. lherefore, the rela'y 525 in the connector' employed in said call will be llt? operatively energized and the cular-dingpo-A tential'on the private contact :2S will come from. ground G* and pass through a resistance similar to the resistance 254 in the switch ll. Upon the second operator com pleting` the operation for the last digit and the wipers coming' to rest, the side switch wipers will, of course, be in second position and circuit will be closed -from the contact 23 through the private wiper 43, side switch wiper 48, springs 199 and 196 and through the relay 200 to battery B. The relay Q00 becomes energized and closesl a circuit through the busy relay 54 from ground G21 tit through. the' springs 202 and 201, through said relay contact ot' springs 20a and 203, relay 1.22 and the private magnet 50 to battery vl Upon the relay energizing, the snring 1Q@ breaks contact with the spring 199 and makes contact' with the spring 197, 'which action, as is well known, locks the side switch in second position. This action also closes the circuit ott the relay 5?, said circuit being traced from the guarding potential` on the private contact 23 (which, it will be remembered, passes through a resistance in the connector side switch wiper 4:8), relay 53, springs 105 andjltl'l, 107 and 196 and the relay 200 to battery itl Although the circuit of the relay i. closed, the resistance tl'ng'ough which the/ guarding potential passes straft sutlicient current to pass through said 1" p :ay to operatively enes gize it, The s'ir ugs and 206 are also pressed together Iwhen the relay 54: is engaged, thereby connecting the. busy tone to the line. The circuit of the busy signaling current is completed from ground through the secondary winding of the busy signaltoo high to Ying machine Q, through the springs 207 and 208, 205 and 20G to the second position of the side switch wiper 4'?, condenser 209, thence over the heavy conductors to the calling line and back over the other side of the line, through the upper windingl ot' relay 51 to battery E and ground G back to the signaling machine Q. ln order to determine whether or not the called line is busy with a. long distance call, the operator operates the key Kg (Fig. L1) to connect hentalkmg set with the line after the connect-ion 1s completed, whereby a patlrof the busy signaling current 'furnished through the operatorie receiver. Upon receiving the busy signal, the operator 'knows at once that'the party she is trying to reach is engaged 1n a long distance call; she informs the calling subscriber that the called line is busy and immediately removes the plugs l andi2 from their respective jacks.- The calling subscriber hangs up his receiver and the apparatus is returned to normal.

New we will assume that the operator at the cord M is calling an automatic subscriber who is engaged in a local call, z'. e., conversing with another automatic subscriber. lt will be remembered that`when one automatic subscriber calls another automat-ic subscriber7 the relay corresponding to the relay 5L. is not operatively energized owing to the high resistance of the line switching relays v101 and 111 in the switches E and F with which it is' in series. There- Jfore the guarding potential on the private contact 23 does not pass through a resistance such as the resistance 254 in Fig. 3. Thus when the wipers 411, l2 anda?) come to rest upon the operator completing the call, and 'while side switch Wipers are yet in nenas-is second position, the same circuits are closed as were traced when the operator called a subscriber who was engaged in a long distance call, except that there will be no resistance 254 in series with the relay 53. Therefore sutlicient current is permitted to flow through said relay to operatively energize it, thereby shifting the spring 208 out of connection with the spring-20T and into contact with the spring 210. The springs 211 and 212 are also pressed together'. Upon the transfer of the spring- 208, the busy machine Q is cut Jfrom the conductor 108 and said conductor is connected to the line of the called subscriber, which connection is tracedv from the side switch wiper 117 l(in second position), springs 20G and 205, 208 land 210 and the conductor 102. Upon the springs 211 and 212 being pressed together, connect-ion is extended from thc second position ot side switch wiper lo to the conductor 190. Therefore it is seen that upon an operi-'for calling a busy automatic subscriber engaged in a local call, no busy signal is given and her talking circuit is cut through. 4She can then inform the subscriber that a long distance call awaits his attention. Should an automatic sul'iscriber find the desired line busy, he would get the busy tone signal, whether 'the calling party be engaged in a. local or .long dist-ance call, for the relay "'l would not be operatively DO energized for reasons heretofore stated.

Therefore the circuit of the relay 53 would l he kept open, thereby preventing the talking circuit from being cut through to 'the called subscribers line and keeping the busy machine Q connected to the second position ot side switch wiper i1-7. Tn the instance of the former kind of call, e., an operator calling a subscriber engaged in' a local call, should the subscribers already engaged in conversation release their connection just as the operators connection is cut through to interrupt said conversation, the. guarding potental would be taken from the contact 23, thereby breaking the circuit including the relays and 200 and said relays would deenergize and break the circuit of the relays 54 and 122 and the magnet 50., tlhe side switch would then pass to third position andr the new connection would be extended to ,the called line and ring the bell. Owing to the relay 53 being slow acting-that is, slow to denergize after-'the circuit is broken--the circuit of the relays 54.-, 122 'andt and 220, relay 54, springs 20s'- and 203, relay 122 and the magnet 50i to battery B. 'lhc nobject of this arrangement is to give the local connection additional time in which to completely release before the private niag- CIK incase-e The relay is prevented troni energizing because the relay 53 cannot energize through the highuresistance in the trunkrelease circuit. Fuitherinorey it is obvious that in this system a toll operator cannot 'all a line which is busy by reason oi having been called by a toll operator, but can nialte connection with a line which is busy by reason of 'having' been called by a local subscriber'. ln the former case the relay 53 niustnot operatively energize even though the relay 53" is energized, and this -is prevented by the resistance 25%. ln the latter cese the relay nuist pull up in order to cut a calling toll operators line through to the called line, notifithstanding the fact that the cutting oli relay is energized, to enable the ope ator to notify one of the two local si'lbscribers that a toll connection is waiting for him.

While have illustrated and described my invention in connection withapparatus of a particular type, it will, of course7 be understood that l do not Wish to liinit inyselt' to the exact construction shown. anddescribcd. in place of the ordinary line switch and selectors shon'n any suitable apparatus could euiployed for extending" the con nection to the connector. Likewise, instead ot ha ving the local connection a purely auto meticconnection, it would, ci course be established by semi-automatic i'neans-that is, through ineens which are partly manual and pertly automat-ic. lin such arrangement. it would be nierely necessary that the selector employed by the operator at the toll-board be a different selector than that employed by the operator at the other inennel positions. Various other inodilications and changes will readily suggest themselves to '-zl'iose skilled in theart end come within the contemplated scope of my invention.

lllhat l claire as my invention is t,

l. telephone system, a called line, e, connector switch for seizinc seid line, a plurelity of means tor extending connection to said connector switch, a second connector" switch, means for: operating said second connector switch to lind seid called line., ncans for. preventing said second connector switch from establishing a talking circuit with tlc called line when one of said :means has been employed 'to entend connection to first connector switch and ineens for ng the operator 'with the re when a. connection les heenk estgflbhsoed completing a talking circuit through seid second connector switch to the called line when the second of said ineens has been ernployed Jfor extending connection to said iL connector switch A .in a telepl'ione systenn a ceiling; nie/nucl line. a, calling` autoinatic line7 a called autonun-ic line` an automatic connector switch, means for extending: connectionvitroin said manual line to said connector switchineans for extending a connection from said calling `automatic line to said connector switch.` 7

means for operating said connectm` to seize said called line, a second connector switch, means for operating; said second connector switchto find said called line, ineens for preventing a talking' circuit being; established through said second connector to the called line when connection has been established with said called line through said first connector switch from the calling inanual line, and means for completing a talking; circuit through said second connector switch to the called line when a connection has been established i Yith the called line through said vfirst connector switch rointhe callingu automatic line.

it ln a telephone System, a plurality of calling lines a celled line, an 'automatic connector switch, means for ciotendingv a connection 'from one or" said lines to said connector switch, means for extending a connection from enother ot said calling; lines to said switch, means for operating said switch to seize said called line7 a second 'connector switch7 ineens, for ope-rating said second coi/inector switch to iind the called linefmeans for preventing said second corr nector switch from establishing a talking circuit Vith the called line when said called line is in connection with one of said calling lines, and means for completing a talking' circuit thri'mgh said connector to said called line when said called line is connected with a second of'said calling,l lines.

l, ln a te ephone system7 a pair ot calling; lines, a called line, enzautornatic connector switch, nieans includingga selector switch for extending av connection from one ot said calling lines to sail connector switch,inea.ns including; another selector switch for tendine' a connection from the second of seid. callinglines to said connector switch, ineens for then operating said conr'i'ector to seize said called line, a` second connector s'wi ineens for operating said second connector vwitch to find said calle preventing;` Asaid second connector switch troni establishing' a talking cir-cuit with saidv called line when the connection hss heen es tablished 'with said called line from said first-mentioned selector, means for con? pleting a talking circuit throngh said ond connector switch to said oel-led line, means for ficy ` lished from said selector to the connector, said connector relay being adapted to be opera- ,groups to said connector,

.groups to said connector,

said called line from said second-mentioned vtorextending a connection from a line of one of said groups to said connector, means including another selector for extending a connection from a line of the other of said groups to said connector, a marginal relay in said connectora low resistance relay in one of said selectors and a -high resistance relay in the other of said selectors, means for connecting' the relay of one of said selectorsl in seriese with the connector relay when a connection is established from said selector to the connector, said connector relay being adapted to be operatively energized when connected in series with said low resistance relay, but not when connected in series with said high resistance relay, and means controlled by enabling said connector to ing circuit with a busy linac.

6. In a telephone system, two groups of lines, an automatic connector switch for connectinggvith the lines of one of means'including a selector switch for extending :reconnection from a line of one of said groups tosaid connector, means including another selector for extending a connection fromvaline of the 'other of said a marginal relay resistance release reestablish a, talk 1n said connector, a low lay in one of said selectors and a high resist-v ance release relay in the other of said selectors, means for connecting the release relay of one of said selectors in series withthe connector relay when a connection is estabtively energized when: connected in series with said low resistance releasev relay, but not when connected in series with'said high resistance release relay, and means controlled by said connector relay for enabling said connector to establish a talking circuit with a busy line.

7. Ina telephone system, a plurality of groups of subscribers lines, an automatic connector switch having motion in one plane to select groups and motion right-angles thereto to iid aline in a selected group, means including a selector' switch for extending a connection from a line of one of said groups to said connector, means including another selector for extending a con nection from a line of the other of said a marginal relay in said connector, a low resistance relay in one of said selectors and a high resistance relay iii the other oi said selectors, means for connecting the relay of one of said selectors in series with the connector relay when a said connector relay for said groups, y

in a plane at' incassa said high resistance relay, and means con'- c trolled by said connector relay for enabling said connector to establish a talking circuit with a busy line.

8. In a telephone system, a plurality of groups of subscribers lines, an automatic c onnector switch having motion in one plane to select groups and motion in a plane at right-angles thereto to iind a line in a selected group, means including a selector switch for extending a connection from a line oil one oic said groups to said connector, means' including another selector for extending a connection from a line oi the other of said groups to said connector, a marginal relay in said connector, a low resistance release relay in one of said selectors and a high resistance release reiay in the other of said'selectors, means for connecting the release relay of one of said selectors in series with the connector relay when aconnection is established from said selector to said connector, said connector relay being adapted to beI operatively energized when connected in series with s'aid low resistance release relay, but not when connected in series with said high resistance release relay, and means controlled by said connector relay for enabling said connector to establish a talking circuit with a busy line.

9. ln a telephone system, lines, an automatic connector necting with the lines ot' one of said groups, means including a selector switch for extending a connection from a line of one of said groups to said connector, means including another' selector for extending a connection from a line oi the other of said groups to said connector, a marginal relay in said connector, a low resistance relay in one of said selectors and a high resistance relay in the other o't' said selectors, means for connecting the relay of one of said selectors in series with the connector relay when a connection is established from said selector' to the connector, said connector relay being adapted to be operatively encrgized when connected in' series with said low resistance relay, but not when connected in series with said high resistance relay, and means controlled by the enci-gization of said connector relay for enabling said connector to establish a talking circuit with a busy line.

10. ln a telephone system, two groups of lilies, an automatic connector switch for connecting with the lines oi one oi" said groups,

two groups ot' switch for ron- -ineans including a selector switch for exonc of said lOO

Mio

Lacasse ing another selector for extending a connection from a line of the other of said groups to said connector, a marginal relay in said connector, a low resistance release relay in one of said selectors and a high resistance release relay in the other el' said selectors, means for connecting the release relay of one et said selectors in series with the eonnector relay when a connection is established from said selector to the connector, said connector relay being adapted to be. operatively energized when connected in series with said low resistance release relay, but not when connected in series with said high resistance release relay, and means controlled by the -energization of said connector relay to tit enabling said connector to establish a talking circuit with a lousy line.

1l. ln a telephone system, a plurality of groups et subscribers lines, an automatic connector switch having motion in one plane to select groups and motion ina plane at right-ang1es thereto to ind a. line in a selected group, means y including a selector switch for extending a connection from a line of one of said groups to said connector', means including another selector tor extend.- ing a connection from a line of the other of said groups to said connector` a marginal relay in said connector, a low resistance relay in one ol' said selectors and a high resistance relay in the other of Isaid selectors, means for connecting the relay of one of said selectors in series with vthe conector relay when a connection is established from said selector to the connector, said connector relay being adapted to be operatively energized when connected in series with said low resistance relay, but not when connected in series with said high resistance relay7 and means controlled ley tli'e energization of Said connector relay for enabling said connector to establish a talking circuit with a busy line.

12. In a telephone system, a plurality of groups of subscribers lines7 an automatic connector switch having motion in one plane to select groups'and motion in a plane at right-angles thereto to find a line in a select-ed group, means including a. selector switch for extending a connection from a line of one of said groups to said connector,

lmeans .including another selefnor for extending a COIHlection from line ofthe other of said groups to said connector, a marginal relay in said connector, a low resistance release relay in one of said selectors and a. high `resistance release .relay in the other of said, selectors, means for connecting the release relay of one of said selectors in series with the connector relay when a connection isestahlished from selector to said con.- nector, said connector relay being adapted. to be operatively energized when connected. in

series 'with said low resistance release relay7 but not when connected in series with.

`then closingsaid normally open switch lo complete the connection with the line when said line is idle. means lor locking' said wipers on said line and n'iaintaining said l switch open when said line is busy, a inarginal relay, means tor closing a circuit through said marginal relay when connection is made with a busy line, means for varying the amount or current flowing through said relay iinlepcndent of the busy line with'which connection is made whereby the relay will energize sometimes when a connector calls a line and sometimes not when the saine line is called, and means controlled by said relay for clo;-;ina circuit around said switch to thereby complete the connection ironi said trunlt to a busy line.

lef. ln a telephone system, a plurality of subscribers lines, means for establishing a connection between two et said lines, said means including a trunk line and a connector switch connected thereto, said connectorincludingline wipers normally disconnected from said trunk, an operating magnet operatively connected with said trunk for moving said wipers to select a group, a second operating magnet normally disconnected 'from said trunk for moving said wipers to con* neet with a line in the selected group, a side switch having a plurality 'of operative posi-4 tions or successively controlling the connection to said operating magnets and then closing the connection from said line Wipers to said trunk, means yfor locking said Wipers on a busy line and for niantaining said side switch in aposition to maintain the connection through the saine to said line wipers open, a marginal relay, means for closings lines divided into groups, a connector Switch having motion in one plane to select groups and motion in a plane at right-angles thereto to connect with a line in a selected group, a plurality of ineens for extending a con lll) Mii)

' means for completing ncction from a calling line to said connector switch, a second connector switch, means for operating said second connector switch to tind said called lim-,ineaus torprcventingsaid second connector switch `trom establishing` a talking circuit with the called line when one of .said means has been employed to extend connection to the first connector switch, and means for completing a talking circuit through said second connector switch to the called line when the second of said means has been employed ior extending connection to said tirst connector switch.

lo. ln a telephone system, manual lines, a plurality of groups olf automatic lines, an automatic connector switch having motion in one plane toselect groups and motion in a plane at, right-angles thereto to connect with a line in a. selected groul), means for extending a connection t'rom said manual lines to said. connector switch, means for extending a connection from said automatic lines to said connector switch, a second con` nector switch, means 't'or ond connector switch to lind said called line, means for preventing a talking circuit being established through said second connector to the called line when connection has been es` tablished with said called line through said first connector switch from the calling manual line, and means for completing a talking circuit through said second connector switch to the c: lled line when a connection has been established with the called line through said tirst connector switch from the calling automatic lines.

17. ln a telephone system, a plurality of groups of lines, an 'automatic connector switch having motion in one plane to select groups and motion in a plano at right-angles thereto to find a line in a selected group, means including` a selector switch for extending a connection from one of said groups of lines to said connector switch, means including another selector switch for extending a connection from a second of said groups oir' lines to said connector switch, a second connector switch, means for operating said second connector switch to find said called line, mea-ns for preventing said second connector switch from establishing a talking circuit with the called line when one of said means has been employed to extend connection to the first connector switch, and a talking circuit through said second connector switch to the called line when the second of said means ,has been employed :t'or extendingconnection to said first connectorswitch.

I8. In a telephone system, a group ot manual lines, a plurality7 of groups of automatici lines, an automatic connector switch having motion 1n one plane to select groups of auto matic lines and motion in a plane at rightoperating said Secing when connection is made with a angles thereto to find a line in a selected group, means including an operators cord circuit tor extending a connection from one of said manual lilies to said connector switch,` means including a plurality of automatic switches' for extending a con-,iection from one of said automatic lines to said connector switch, a second connector switch, means tor preventing said second connector switch from establishing a connection with a called line when connection has been established thereto from one of said manual lines, and means for establishing a talking circuit with said called line when said second connector makes connection therewith when connec tion has beenestablished with said called line from one of said automatic lines through said first-mentioned connector.

19. In a telephone systeni, a called line provided with multiple terminals, a connector switch for seizing said line, a plurality oiz means tor extending a connection to said connector switch, means in said connector for placing one guarding potential on said multiple terminals when one ot' said means is employed to extenod a connection to said connector, means in said connector for placing a second guarding potential on said multiple terminals when the second oit' said means employed t'or extending connection to said connector switch, and means in said connector operative when an attempt is made to establish a connection with a busy line and responsive to but one of said guarding potentials for enabling said connector switch to establish a talking connection with said busy line. 20. In a telephone system, a called line provided with multiple terminals, a connector switclrfor seizing said linie, a plurality ot' means for extending a connection to said connector switch, a connection in said con; nector for connecting' said multiple terminals through to ground when said connector seizes the called line, a relay in said connector, means for energizing said relay when connection is established with said connector through one of said means, means controlled by the energization of'said relay for placing a resistance in said guarding ground connection to said multiple terminals, a marginal relay in' said connector adapted to be connected in circuit with said multiple terminals when connection is made -with a lousy line, said marginal relay being adapted to respond only when connection is made with a busy line whose multiple terminals are connected to ground direct, but not respondi busy line whose multiple terminals are connected to ground through a resistance, and means controlled by said marginal relay for completing a talking circuit to the busy line.

2l, "In a telephone system, twogroups of iis sacaste lines, an automatic connector switch for connecting with the lines of one ci' said groups, means including a selector switch for extending a connection from a line of one of said groups to said connector, means including another selector for extending a connection from a line oie the other of said groups to said connector, a marginal relay in said connector, a low resistance'relay in one of said selectors and a high resistance relayin the other of said selectors, means for connecting the relay of one of said selectors in series with the connector relay when a connection is established from said selector to the connector, said connector relay being adapted to be operatively energized vwhen connected in series with said low resistance relay, but not when connected in series with said high resistance relay, means for establishing a guarding potential on the multiple contacts of a called line by establishing a connection to ground through said connector when said connector seizes the called line, means controlled by the energization of said marginal relay for inserting a resistance in said ground connection to thereby lower the guarding `potential on the multiple contacts oi' the called line, a second marginal relay in said connector adapted to be connected in circuit with multiple con# tacts of the called line, said second relay adapted to be energized when said connector Y attempts to make connection with a busy line whose multiple contacts are provided with a guarding potential trom a direct ground, but not energized when the multiple contacts are provided with a guarding poten` tial through a Vresistance to ground, and

means controlled by the energization of said second marginal relay for completing a talking connection to the busy called line.

22. ln a telephone system, a called line, a connector switch for seizing said line, a plurality of means for extending connection to said connector switch, a second connector switch, a plurality of means 'or extending connection to said second connector switch, means for operating said second connector switch to i'ind said called line, means opera? tive when one of said means has been used .to extend connection to said second connector switch to prevent said second connector from completing a, talking circuit to said called line when either of said means has been used for extending connection to said first connector switch, and means operative when the other means has been used for extending connection to said second connector switch to prevent said second connector switch from completing a talking circuit to the called line whenl one of the means has been used 'for extending connection to the first connector switch, but permitting a talking circuit to be Iclosed with the called line when the other means has been used to obtain connection switch.

23. In a. telephone system, a called line provided with multiple terminals, a connector switch for seizing said line, a plurality of means for-extending a connection to said connector switch, means in said connector for placing one guarding potential upon with the rst connector said multiple terminals when one of said means is employedto extend a connection to said connector, means in said connector for placing a second guarding potential on said multiple terminals when the second of said means is employed for extending connection to said. connector switch, and means in said connector responsive to either of said guarding potentials to prevent a connection With a busy line when one means has been employed to extend connection tol said connector, and responsive to but one of said guarding potentials to prevent a connection with i a. busy line When the other means has been the called line busy to further calls from one group only and responsive to the other potential to make the called line busy to further calls from either group.

25. In a telephone system, a group of lines, a second group of lines, a called line, means for connecting a subscriber of either group with said called line, a circuit for applying avpotential of one kind to the called line when the call is from one group, a relay controlling said circuit, another circuit for applying a potential of another kind to the called line when the call is 'from another' group, and means responsive to one potential to make the called line busy to further calls from one group only and responsive to the other potential to make the called line busy to tui-ther calls from either group.

26. In a telephone system, a groupof lines, a Second group of lines, a called line, means for connecting a subscriber of either group with saidcallcdliue, a circuit i'or applying `a potential o't' one kind to the called line when the call is ii'om one group, another circuit for applying a potential ot another kind to the called lnc when the call is from the other group, a muguet controlling said circuits, and means responsive to one poten- .tial to make the called line busy to further calls from one group only aud responsive to the other potential to makithc called liuc busy to further calls from either group.

group and responsive to the other potential to make the called line busy to further calls from either group.

28. ln a telephone system, a group ot lines, a second `group of lines, a called line, means for connecting a. subscriber of either group ivith said called line` a circuit for applying a potential of one kind to the called line when the call is from one group, another circuit t'or applying a potential of another kind to the called line when the call is from another group, a relay controlling said circuits, and means responsive to one poten tial toinake the called line busy to further calls from one group but accessible t'or talking to the other group and responsiveI to the other potential to make the called line busy to further calls from either group.

29. ln a telephone system. a. group of lines, a second group ot' lines, a called line, means for connecting` a subscriber ol either group ,vith said called line. a circuit t'or applying a potential of one kind to the called line when th'e call is from one group, another circuit 'for applying a potential-ot' another kind to the called line when the call is from the other group, a iinigiiet controlling said circuits, and means responsive to one potential to make the called line busy to further calls rom one, group but. accessible for talking to the other group' and responsive to the other potential to make the called line busy to further calls from either group.

30. In a telephone system, a group of `lines,ay second group of lines, a called line, means for connecting a subscriber of either group with said called line and t'or applying a potential ot' one kind to the calledline When a call is from one group, and fonapplying ay potential ot' another kind tothe called line when the, call is from another group, and ineans comprisiniriV a relay responsive to one potential to make the called line busy to further'calls from one group but accessible tor talking-to the other group and responsive to the other potentialto make the .called line busy to 'further calls from either group.

3l. in. a telephone system. a group of lines, a second `group ot' lines, a called line, means tor connecting a subscriber ot' either group with said called line, and means comprising a circuit for applying a potential of one kind to the called line when the call is 'magnet controlled by essere group with said called line, means comprising a circuit. for applying a potential of one kind to the called line when the call is from one group and comprising also a marginal relay tor cont-,rolling said circuit, means comprising a circuit for applying a potential of another kind t0 the called line when the call is from the other group, and amarginal magnet controlling said circuit, and means comprising a marginal relay responsive to one potential to make the called line busy to further calls from one group but accessible for talking tothe other group and responsive to the other potential to make the the other group and responsive to the called line busy to further calls from either l group.

33. In a telephone system, a line, a Aconnector forestablishing connection with said line, another connector for establishing con* nection Awith said line, circuitsfor each connector. a magnet in the first connector for controlling the circuits thereof, a magnet in the second connector for controlling the circuits thereof, a'second magnet in the second connector for controlling the circuits thereof, an energizing circuit for said second magnet controlled by the other two magnets jointly, and a trunk for extending connection to said second connector and an energizing circuit for said second magnet energized over said trunk.

34. In a telephone system, a line, a. 'connector for establishing connection with said lino, another connector forestablishing connection with said line, circuits for each connector, a magnet in the first connectorfor controlling the circuits thereof, va magnet in the second connector foi-:controllingl the circuits thereof, a second magnet in theseo ondy connector for controlling the circuits thereof, an energizing circuit for said'seoond jointly, trunks t'or extending connections to said connectors, said first magnet. energized over one ot' said trunks and said second magnet energized over one of said trunks.

35. In a telephone system, a line, a switch tor establishing connection with said line, a guardingcircuit for said line, a magnet in said switch for applying either of two potentials to said guarding circuit, a second switch for establishing connection `With said guarding potential, means in said second the other two magnets ist Yswitch operable over said guarding circuit i prevent the establishment of a connection with said called line, asecond magnet in said second switch operable by one of the lpoten-- tials in said guarding circuit establishment of a connection withthe called line, acircuit forl said magnet, and a third magnet in said secondswitch for controlling the circuit of said second magnet.

36. 'In a telephone system,.a line a switch4 for vestablishing v'connection with said line, a guarding otential circuit for said line, means in said switch for' establishing one of two, potentials vin saidguarding c1rc'uit,f

a second switch, means in said second switch ffor calling the said line and for establishing connection with said guarding Jcircuit, means in said second switch for preventing the establishment of a talking circuit lwith the said for establishing connection with said line, a

j connection with .guarding potential circuit for said line,

means in said switch for establishing. one of two potentials in said guarding circuit, a second switch, meansin said second switch for calling the said line and lfor establishing said guarding. circuit, means in said second switchforpreventing the esing circuit'for estab I'- switch for' controlling 40 tablishment of a talking circuit with lthe said line, a'magnet in sai second switch operable by one of the otentials in said guardishiiig a talkin circuit line, and means in sai second the circuit of said magnet, and a trunk line for extending connection tov said irst switch.

38. In atelephone system, a line, a switch for establishingconnection'with said line, a guarding potential circuit for said line, means in said switch for establishing lone of' two potentials in said guarding circuit, a second switch, means in said second switch with said for calliiig the said line and for establishing connection with said'guarding'circuit, means in said second switch for preventing the establishment of a talking circuit with the said line, a magnet in said second switch o by one of the otentials in-said guarding circuit for establlishing a talking circuit with said line, and means in said second switch tor controlling the circuit of said magnet, a

to cause the meansin said switch 'for establishin ishing'a talking circuit with erable s an tiiunk line for extending connection to said first switch, said first means comprising a magnet, an 'energizing circuit for 'said inagnet, and means for energizing said vmagnet over said trunk.

- 39. In a telephone system, a line,l a switch' for establishing connection with said line, a guarding potential circuit for said line one of two potentials in said guarding circuit, a second switch, means in said second switch for calling the Said lineand for establishing i connection with said guarding circuit, means,

uin said second switch for preventing the estlzirblishment of a talking circuit 'with'the said e by .one of the potentials in said` guardin circuit for establishing a talking circuit wit 4 said line, and means in said sec'ond switch `for controlling the circuit .of vsaid magnet,

means for extending connection Ato-said scc, I

ond switch, said means comprising' a magnet an energizing circuit for said magnet an means for energizing saidmagnet over said trunk.

' 40. In a telephone'system, a line, a switch for establishing connection with said line, a guarding potential circuit for saidline,

means in said switch for establishing one of two potentials in said guarding circuit, a second swi ch, means in said second switch for lcalling the said line and for esa magnet in said second switch operable tablishing connection with said'. guarding circuit, means in said second switch for preventing the establishment cfa talking circuit with the said line, a magnet in said second switch operableby one of the potentials in i said guardin circuit for establishing a. talking circuit with said line, and means in said second switch for controlling the circuit of said magnet, ay trunk line for extending connection to said first switch, said first means comprising a magnet an .energizing circuit for said magnet, means florenergizing said magnet over said trunk, a trunk for extending connection to said second switch, said last means comprising a magnet, an energizing circuit for said magnet and means 'for energizing said magnet over said last trunk. Signed by me at Chicago, Cook county, Illinois, this 9th day of June, 1913. 

